Concrete Curvy beds – Are these Green?

STAYING HOME. We have decided to go on holiday, and like the majority of people in our culture, we decided to have a carbon footprint to add to our holiday joy. We thought about a plane trip somewhere wonderful… but there was no place to go that was as beautiful as our own home. We thought of a tent camping trip through the Rockies, but the last time we did that we saw slopes of climate ravaged dead pine and way too many luxury RVs. So we figured out a way to play the carbon footprint game right here at home. A way we could do our part to feel like one of the gang.

View to zone 1 from front door.

Bring on the CONCRETE (and sarcasm). We decided to make raised garden beds at the front of the house, and we chose to use the highest carbon footprint construction material we could get our hands on. Woohoo! After all, if you are going to pump greenhouse gases into the air, you might as well do it right the first time. So we thought we would skip the cedar and move right into the concrete. The carbon emitted from the concrete industry is like putting the atmosphere on crack(ed) and fracked greenhouse gas.

Cedar as option 1. Our first option was wooden beds. Not fancy, but O’NATURAL. It seems more eco… (and usually is). Based on our experience, we would have to replace the beds every 6 years or so, and there was concern over disturbing the perennials we had planned on planting – olive, persimmon, tumeric, lemon, and ginger. We also thought about getting older and having to rebuild it too many times over our short lives. We thought cedar would be a lower carbon footprint… but dammit, we wanted permanence and concrete.

Ann contemplating the carbon footprint.

This is what we found when Gord put his nerdy hat on. Basing our calculations on 240 board feet of red cedar, that pre-milled comes in at a weight (based on 12% moisture) of approx 453 kg, with a carbon footprint of 0.119 kg/kg, means the beds would account for 54.74 kg of ghg equivalents (GHGe). This does not include nails, metal brackets, or anchors that would be required to assemble and anchor it to the ground – add in 5 kg of metal at a multiplier of 4.0 kg and you can add another 20 kg of GHGe for a one time total of 74.74 kg GHGe. Now, based on replacing them every 6 years (from experience with our other beds), we would expect to go through 6 replacement cycles over our life span (Gord being 83). This equates to 448 kg of GHGe attached with the front beds over time. This does not account for the time and effort it takes to remove the plants that have been established, rebuild the beds, and replant – consuming probably 4 – 5 days of labour each time. (and the extra beer consumed). There is one additional caveat to this calculation as most embodied GHGe equations addressing wood carbon footprint do not include the carbon sequestered in the wood – for every m3 of cedar there is 632 kg of carbon stored… that is released upon decay. In our above scenario we are dealing with 0.566 m3 (357 kg of carbon) which could be assumed to release 20% of its store every 6 years (357 X 20% X 6 = 428 kg of carbon over its life span). The real number of the GHGe over its lifespan could be closer to 876 kg. CEDAR OPTION = 0.876 tonnes of GHG’s

Homemade lime “el fresco” paint made with earth pigments

Concrete. Ann and I are not fond of concrete strictly due to its impact on the environment. With our evil Dr. Evil hats on our head, it would seem logical that concrete may be the easiest for us yet the worst environmental solution.

We used 341 kg of portland cement at a carbon footprint of 272 kg of GHGe. Add 40 kg of metal lath and steel rod (combined) with a GHGe of 160kg, and the sand 2267 kg which has a GHGe of approx 5 kg, and the total GHGe would be 436 kg. CONCRETE OPTION = 0.436 tonnes of GHG’s

Beauty and function to last a LONG time…just like the cob house.

And the WINNER IS CONCRETE. So over a period of 36 years, between the two options, the option with a lower initial carbon footprint and the one with the larger, get flipped on their head. Where they differ is that the beds of concrete will continue to produce food past our life time, and hence will have been a better carbon investment. The concrete also adds to the thermal mass to create a micro climate on the south wall of the cob house – thus we can grow turmeric, ginger, olives, lemons, and MORE WINTER VEGGIES.

Gord contemplating his carbon footprint.

We are not justifying the use of concrete in no way, as concrete used to an excess without care, and without a long term vision is a frivilous waste of carbon. This is so clearly prevalent when we look to its use in the various bridges and buildings built with life spans of 30-40 years (BC Place Stadium; bridges crumbling in Quebec), monster homes, and much of the indulgent infrastructure in our civilzation. Excess use is not the point I am driving home, but instead conscientious use… appropriate technology for the job.

OUR CARBON FOOTPRINT. We have had many discussions over the years of what it would take for us to further reduce our personal carbon footprint (which is between 3-4 tonnes each. Canadian average is about 20 tonnes). We would have to give up technology (like computers, pumps, solar panels, etc); household appliances (like washing machine, propane stove, etc); workshop tools like table saw, drills, mitre saws, planer, sander, grinder, etc), and of course our farm truck and diesel smart car and COFFEE. OMG…not the coffee. All of this would mean we would no longer be able to be a farm selling perennial edible permaculture plants, we could not be on muncipal council without a car or computer and especially the coffee, and we could not even clean the public composting toilet (as we bring the humanure here in the truck to compost). So in summary, we are just as trapped in this civilization as as everyone else (which is why the SYSTEM needs to change). So, we continue on growing most of our food, helping others grow food, give our tours, teach, consult about better ecological design, and bring many new conversations to the council table as we help to set local and greener policies to impact as much as we possibly can.

So maybe we failed; maybe we impacted the climate; maybe we created awareness? We don’t know. Maybe next time we’ll choose the option thatpromotes the clear cut of old growth cedar to achieve our mischievous deeds. Or maybe grow some black locust which lasts much longer than cedar and grows faster AND it feeds the soil with nitrogen…but alas, black locust is invasive. Always pros and cons.

PS: We did consider stone, and did not include this in the update. The use of it would actually involve about similar concrete usage in the creation of the foundation and the mortar. YOUTUBE videos of the process Part 1 and Part 2.

We co-created an abundant, biologically diverse, and beautiful home that is a “being in place”.

2 responses to “Concrete Curvy beds – Are these Green?”

I think you referred to the ‘curvy sheets’ you used in a previous posting when you first began creating curvy bed-making a while back. Could you post a reference to that earlier posting please? What are those ‘sheets’ made of?

Ummm…. what would be the net result if you had planted x cedars in advance of each rebuild? or better still planted the total in advance of the build. Certainly they would not initially do much to negate or offset the GHG’s…. but down the line… where as concrete …never going to “payback”